1. Field of the Invention
The present invention relates to a method and apparatus for creating data carousels, in particular providing a user who has a particular file structure in mind with an easy mechanism by which to create and optimise appropriate data carousels.
2. Description of the Related Art
A data carousel may be created by developing new data or editing existing data.
For instance as part of a DVB compliant system, it is known to provide an information server for broadcasting any form of data, such as MHEG5 applications, HTML pages, Java applications, IRD software upgrades and other data services in the form of DSMCC objects on data carousels. An IRD is an Integrated Receiver Decoder and this term is used in standards documents to describe devices capable of receiving and decoding digital streams, eg. set top boxes and integrated digital TV sets.
Raw data may be divided into appropriate DSI (Download Server Initiate), DII (Download Information Indication) or DDB (Download Data Block) sections for insertion into MPEG transport stream packets as a data carousel. These are three types of messages defined in DSM-CC that carry the structure of a data carousel in the broadcast stream. In fact, DSI, DII and DDB are “messages” but “DSI section” is used to describe a MPEG section carrying a DSI message. Sections are split into packets, the lowest level structure in the stream. A data carousel is the collection of DSI, DII and DDB messages.
Alternatively, however, a user may determine a desired file structure for an object carousel consisting of files, directories and other object types. In DSM-CC there are five object types in an object carousel, namely Files, Directories, a Service Gateway, Streams and StreamEvents. These can all exist in the hierarchical structure that is like a filesystem. It is then a non trivial matter to rearrange the data of the object carousel into DSI, DII and DDB sections in an optimised manner for broadcast as a data carousel. There are many possible data carousel structures that can represent a given object carousel. It is desirable to choose an optimal data carousel that will be most effective by using knowledge of the intended use for the files in the object carousel and knowledge of the receiving equipment, but some experimentation is required to achieve this optimisation. Each time the user wishes to make alterations to the file structure on which the object carousel is based, it is necessary to reconsider entirely the structure of the corresponding data carousel.